behnaz alafchi | Hamadan Medical University (original) (raw)

Papers by behnaz alafchi

Computer Modeling in Engineering & Sciences

Survival data with a multi-state structure are frequently observed in follow-up studies. An analy... more Survival data with a multi-state structure are frequently observed in follow-up studies. An analytic approach based on a multi-state model (MSM) should be used in longitudinal health studies in which a patient experiences a sequence of clinical progression events. One main objective in the MSM framework is variable selection, where attempts are made to identify the risk factors associated with the transition hazard rates or probabilities of disease progression. The usual variable selection methods, including stepwise and penalized methods, do not provide information about the importance of variables. In this context, we present a two-step algorithm to evaluate the importance of variables for multi-state data. Three different machine learning approaches (random forest, gradient boosting, and neural network) as the most widely used methods are considered to estimate the variable importance in order to identify the factors affecting disease progression and rank these factors according to their importance. The performance of our proposed methods is validated by simulation and applied to the COVID-19 data set. The results revealed that the proposed two-stage method has promising performance for estimating variable importance.

JPO Journal of Prosthetics and Orthotics, 2022

BACKGROUND Metabolic syndrome (MetS), a major contributor to cardiovascular disease and diabetes,... more BACKGROUND Metabolic syndrome (MetS), a major contributor to cardiovascular disease and diabetes, is considered to be among the most common public health problems worldwide. OBJECTIVE We aimed to identify and rank the most important nutritional and nonnutritional factors contributing to the development of MetS using a data-mining method. METHODS This prospective study was performed on 3048 adults (aged ≥20 years) who participated in the fifth follow-up examination of the Tehran Lipid and Glucose Study, who were followed for 3 years. MetS was defined according to the modified definition of the National Cholesterol Education Program/Adult Treatment Panel III. The importance of variables was obtained by the training set using the random forest model for determining factors with the greatest contribution to developing MetS. RESULTS Among the 3048 participants, 701 (22.9%) developed MetS during the study period. The mean age of the participants was 44.3 years (SD 11.8). The total inciden...

Iranian Journal of Public Health

Background: Breast cancer is the first non-cutaneous malignancy in women and the second cause of ... more Background: Breast cancer is the first non-cutaneous malignancy in women and the second cause of death due to cancer all over the world. There are situations where researchers are interested in dynamic prediction of survival of patients where traditional models might fail to achieve this goal. We aimed to use a dynamic prediction model in analyzing survival of breast cancer patients. Methods: We used a data set originates from a retrospective cohort (registry-based) study conducted in 2014 in Tehran, Iran, information of 550 patients were available analyzed. A method of landmarking was utilized for dynamic prediction of survival of the patients. The criteria of time-dependent area under the curve and prediction error curve were used to evaluate the performance of the model. Results: An index of risk score (prognostic index) was calculated according to the available covariates based on Cox proportional hazards. Therefore, hazard of dying for a high-risk patient with breast cancer wit...

Journal of Probability and Statistics, 2021

In longitudinal studies, clinicians usually collect longitudinal biomarkers’ measurements over ti... more In longitudinal studies, clinicians usually collect longitudinal biomarkers’ measurements over time until an event such as recovery, disease relapse, or death occurs. Joint modeling approaches are increasingly used to study the association between one longitudinal and one survival outcome. However, in practice, a patient may experience multiple disease progression events successively. So instead of modeling of a single event, progression of the disease as a multistate process should be modeled. On the other hand, in such studies, multivariate longitudinal outcomes may be collected and their association with the survival process is of interest. In the present study, we applied a joint model of various longitudinal biomarkers and transitions between different health statuses in patients who underwent renal transplantation. The full joint likelihood approaches are faced with the complexities in computation of the likelihood. So, here, we have proposed two-stage modeling of multivariate...

JMIR Public Health and Surveillance, 2021

Background Metabolic syndrome (MetS), a major contributor to cardiovascular disease and diabetes,... more Background Metabolic syndrome (MetS), a major contributor to cardiovascular disease and diabetes, is considered to be among the most common public health problems worldwide. Objective We aimed to identify and rank the most important nutritional and nonnutritional factors contributing to the development of MetS using a data-mining method. Methods This prospective study was performed on 3048 adults (aged ≥20 years) who participated in the fifth follow-up examination of the Tehran Lipid and Glucose Study, who were followed for 3 years. MetS was defined according to the modified definition of the National Cholesterol Education Program/Adult Treatment Panel III. The importance of variables was obtained by the training set using the random forest model for determining factors with the greatest contribution to developing MetS. Results Among the 3048 participants, 701 (22.9%) developed MetS during the study period. The mean age of the participants was 44.3 years (SD 11.8). The total inciden...

Background: This study was conducted to better understand the influence of prognostic factors and... more Background: This study was conducted to better understand the influence of prognostic factors and the trend of CD4 cell count on the risk of progression to acquired immunodeficiency syndrome (AIDS) and tuberculosis (TB) infection among patients with human immunodeficiency virus (HIV) in a developing country. Methods: The information of 1530 HIV-infected patients admitted in Behavioral Diseases Counseling Centers, Tehran, Iran, (2004-2014) was analyzed in this study. A joint model of ordinal longitudinal outcome and competing events is used to model longitudinal measurements of CD4 cell count and the risk of TB-infection and AIDS-progression among HIV patients, simultaneously. Results: The results revealed that the trend of CD4 cell count had a significant association with the risk of TB-infection and AIDS-progression (p<0.001). Higher ages (p<0.001), the history of being in prison (p=0.013), receiving antiretroviral therapy (ART) (p<0.001) and isoniazid preventive therapy ...

Background : Bipolar disorder (BD) is a major public health problem. In time series count data th... more Background : Bipolar disorder (BD) is a major public health problem. In time series count data there may be over dispersion, and serial dependency. In such situation some models that can consider the dependency are needed. The purpose current research was to use Poisson hidden Markov model to forecast new monthly BD instances. Methods : In current study the dataset including the frequency of new instances of BD from October 2008 to March 2015 in Hamadan Province, the west of Iran were used. We used Poisson hidden Markov with different number of conditions to determine the best model according to Akaike Information Criterion (AIC) and Bayesian Information Criterion (BIC). Then we used final model to forecast for the next 24 months. Results : Poisson hidden Markov with two states were chosen as the final model. Each component of dependent mixture model explained one of the states. The results showed that the new BD cases is increase over time and due to forecasting results number of p...

Journal of Oral and Maxillofacial Surgery, Medicine, and Pathology

Background Curing of colorectal cancer (CRC) occurs at the time of resection, but it is not immed... more Background Curing of colorectal cancer (CRC) occurs at the time of resection, but it is not immediately observable. If the cancer is not completely eliminated, the patient will not be cured of cancer and will experience a recurrence as the tumor has regrown to a detectable size. The main proposes of the present study was to assess the effects of different covariates on the probability of being cured as well as the time to recurrence, time to death, and time to death after recurrence in CRC patients by using multi-state cure model.Methods In the present study, the information of 283 patients with adenocarcinoma CRC, who underwent resection, from 1992 to 2015 in Imam Khomeini Hospital of Hamadan, Iran, were analyzed. A multi-state cure model is used to joint modeling the recurrence and death in patients with CRC when a fraction of patients was apparently cured after resection.Results The results revealed that females, patients diagnosed at stage IV and whom underwent radiotherapy were less likely to be apparently cured. Also, more than 50% of not cured patients recurred later. Moreover, the survival time of patients was affected by the stage of disease, age at diagnosis and receiving radiation therapy. In addition, sex had a significant effect on the timeto-recurrence.Conclusions The multi-state cure model provided a flexible framework to study and compare the effects of prognostic factors simultaneously on the transition between different health states and the probability of being apparently cured of CRC. Background Colorectal cancer (CRC) is a major cause of mortality and morbidity. It is one of the most commonly diagnosed cancer (1) and the fourth common cause of cancer-related death worldwide (2, 3). The CRC survival is highly dependent upon the stage of disease at diagnosis as well as the possibility of resection of the tumor (7, 8). The only curative treatment for CRC patients is complete surgical resection. About 70% to 80% of patients are eligible for curative resection (9, 10). Moreover, almost two-thirds of CRC patients underwent resection but 30% to 50% of these patients will experience recurrence and will die of CRC

Avicenna Journal of Dental Research

Background: Class II malocclusion is one of the most common orthodontic problems that can be divi... more Background: Class II malocclusion is one of the most common orthodontic problems that can be divided into class II division 1 and division 2. Considering the differences between the 2 malocclusions, the present study was designed to compare the dentoskeletal changes caused by growth modification treatment. Methods: This retrospective study included 52 patients (2 groups) with class II division 1 and 2 malocclusions, who were within the age range of 11-13 years and were treated by growth modification. Initial and final cephalograms were analyzed by Dolphin software premium 11.8. In addition, 7 cephalometric variables including SNA, SNB, ANB, SN-GOGN, inter-incisal angle, mandibular body length, and overbite were measured in traced cephalograms. Finally, treatment changes in each group were analyzed by paired t test and between-group comparison was assessed by independent t test. The significant level was considered as 0.05. Results: Based on the results of dentoskeletal changes in both groups, SNB, ANB, mandibular length, and overbite underwent significant changes during treatment in both groups. Further, the interincisal angle changed significantly in division 2 group (P < 0.0001) and the final interincisal angle decreased significantly in class II division 1 patients (P < 0.025). The results further revealed that changes in SNB and interincisal angles were statistically significantly greater in division 2 group compared to division 1 group (P < 0.021 and P < 0.012, respectively). Finally, there was no statistically significant difference between the groups regarding the other variables. Conclusions: Overall, mandibular position changes more in class II division 2 patients and the treatment appears to be more successful in this group.

Frontiers in Dentistry

Objectives: This study aimed to assess the relationship of frontal sinus height and width with th... more Objectives: This study aimed to assess the relationship of frontal sinus height and width with the cervical vertebral maturation (CVM) for assessment of skeletal maturity. Materials and Methods: This retrospective study evaluated lateral cephalograms of 132 patients between 8 to 21 years, including 66 males and 66 females. For each of the six stages of the CVM, 22 patients (11 males and 11 females) were evaluated. The Ertuk’s method was used to measure the height and width of the frontal sinus. The sinus height to width ratio was calculated and considered as the sinus index. The CVM was evaluated on the same lateral cephalograms using the Baccetti’s method. The correlation of frontal sinus height and width with the CVM was analyzed, and comparisons were made using independent t-test, ANOVA, Mann-Whitney test, and Kendall's tau-b correlation coefficient. Results: The sinus width was 10.85±2.7 mm in males and 9.47±2.6 mm in females. The sinus index was 2.43±0.37 in males and 2.66±...

Pesquisa Brasileira em Odontopediatria e Clínica Integrada

To assess the prevalence of soft tissue calcifications and their panoramic radiographic character... more To assess the prevalence of soft tissue calcifications and their panoramic radiographic characteristics. Material and Methods: This descriptive retrospective study evaluated 2027 panoramic radiographs. The type and location of calcifications and the age and gender of patients were evaluated by two radiologists. Data were analyzed via SPSS and the Chi-square, Fisher's exact and Kappa tests were used to compare the categorical demographic variables among the groups. The confidence interval was set to 95% and p<0.05 was considered statistically significant. Results: The prevalence of calcified stylohyoid ligament was 11.24%. This value was 3.99% for tonsillolith, 1.33% for calcified carotid plaque, 0.69% for antrolith, 0.39% for calcified lymph node, 0.29% for phleboliths, and 0.19% for sialoliths. The prevalence of these conditions had no significant association with gender or age (p=0.102). The prevalence of bilateral calcified stylohyoid ligament, tonsillolith, and a calcified carotid plaque was significantly higher (p<0.001). The most prevalent type of calcified stylohyoid ligament, according to O'Carroll's classification, belonged to types 1, 4, 3 and 2 (p<0.001). The most commonly observed radiographic pattern was multiple, well-defined tonsilloliths (75.3%, p<0.001). Conclusion: The prevalence of soft tissue calcifications on panoramic radiographs was relatively low in this Iranian population. The most calcifications were respectively calcified stylohyoid ligament, tonsillolith, calcified carotid plaque, antrolith, calcified lymph node, phleboliths and sialoliths. Calcified stylohyoid ligament, tonsillolith and calcified carotid plaque were more bilaterally. Thereby panoramic imaging can help in primary assessment, epidemiologic and screening evaluation of these calcifications.

Clinical Epidemiology and Global Health

Asian Pacific Journal of Cancer Prevention

Cancer is the most common chronic disease and the most important causes of death and disability, ... more Cancer is the most common chronic disease and the most important causes of death and disability, worldwide. Cancer after cardiovascular diseases is the second cause of death in the developed countries (del Pilar Díaz et al., 2009) and after cardiovascular diseases and accidents is the third cause of death in Iran (Farahmand et al., 2011). Among all types of cancer, lung cancer is the most common cancer in men and the fourth most frequent cancer in women. The highest rates of lung cancer are seen in West Asia, South Africa, and the Caribbean, among less developed countries with an age-standardized rate (ASR) of 25.7 to 32.2 per 100,000 (Ferlay et al., 2010). From a public health standpoint, development of lung cancer is so worrying because of its worst prognosis (Olsen, 1997). Based on classification of the America Cancer Society according to the type of cells in the lung tissue, there are two types of lung cancer including small cell carcinoma (SCC) and non-small cell carcinoma (NSCC) (Macdonald et al., 2004). The most common type of lung cancer is SCC and about 67% of the all cases which diagnosed with this type have metastatic disease because this type of disease

Epidemiology and health, 2014

With a gradual decline in maternal mortality in recent years in Iran, this study was conducted to... more With a gradual decline in maternal mortality in recent years in Iran, this study was conducted to identify the remaining risk factors for maternal death. This 8-year nested case-control study was conducted in Hamadan Province, in the west of Iran, from April 2006 to March 2014. It included 185 women (37 cases and 148 controls). All maternal deaths that occurred during the study period were considered cases. For every case, four women with a live birth were selected as controls from the same area and date. Conditional logistic regression analysis was performed and the odds ratio (OR) and its 95% confidence interval (CI) were obtained for each risk factor. The majority of cases were aged 20-34 years, died in hospital, and lived in urban areas. The most common causes of death were bleeding, systemic disease, infection, and pre-eclampsia. The OR estimate of maternal death was 8.48 (95% CI=1.26-56.99) for advanced maternal age (≥35 years); 2.10 (95% CI=0.07-65.43) for underweight and 10....

Epidemiology and Health, 2014

OBJECTIVES: With a gradual decline in maternal mortality in recent years in Iran, this study was ... more OBJECTIVES: With a gradual decline in maternal mortality in recent years in Iran, this study was conducted to identify the remaining risk factors for maternal death. METHODS: This 8-year nested case-control study was conducted in Hamadan Province, in the west of Iran, from April 2006 to March 2014. It included 185 women (37 cases and 148 controls). All maternal deaths that occurred during the study period were considered cases. For every case, four women with a live birth were selected as controls from the same area and date. Conditional logistic regression analysis was performed and the odds ratio (OR) and its 95% confidence interval (CI) were obtained for each risk factor. RESULTS: The majority of cases were aged 20-34 years, died in hospital, and lived in urban areas. The most common causes of death were bleeding, systemic disease, infection, and pre-eclampsia. The OR estimate of maternal death was 8.48 (95% CI= 1.26-56.99) for advanced maternal age (≥ 35 years); 2.10 (95% CI= 0.07-65.43) for underweight and 10.99 (95% CI= 1.65-73.22) for overweight or obese women compared to those with normal weight; 1.56 (95% CI= 1.08-2.25) for every unit increase in gravidity compared to those with one gravidity; 1.73 (95% CI= 0.34-8.88) for preterm labors compared to term labors; and 17.54 (95% CI= 2.71-113.42) for women with systemic diseases. CONCLUSIONS: According to our results, advanced maternal age, abnormal body mass index, multiple gravidity, preterm labor, and systemic disease were the main risk factors for maternal death. However, more evidence based on large cohort studies in different settings is required to confirm our results.